1. Field of the Invention
This invention relates to a shielded electrical connector for interconnecting circuitry on a substrate and more particularly it relates to an electrical connector having an elastomeric body which can be positioned between two substrates such as printed circuit boards to interconnect corresponding aligned pads on the printed circuit boards.
2. Description of the Prior Art
U.S. Pat. No. 3,985,413 discloses a miniature unshielded electrical connector which can be positioned between spaced apart substrates, such as printed circuit boards to interconnect circuitry on each of the printed circuit boards. The connector consists of a generally cylindrical elastomeric body having a thin conventionally stable flexible film wrapped around the elastomeric body. Circuit traces are defined on the flexible film and face outwardly. When the elastomeric body is compressed between the two substrates or printed circuit boards, the elastomeric body supplies sufficient compressive force to establish an electrical connection with exposed pads on the printed circuit boards.
The electrical connector disclosed in U.S. Pat. No. 3,985,413 employs a film of polymeric material which is wrapped around the elastomeric body. The free ends of the film are joined together to maintain the film in surrounding relationship to the elastomeric body. The fim is not attached directly to the elastomeric body, thus permitting relative movement therebetween when the body is placed under compressive loads.
U.S. Pat. No. 3,985,413 only discloses the elastomeric connector and does not describe the manner in which that elastomeric connector is mounted to interconnect separate circuit components, such as printed circuit boards. In use, that miniature electrical connector must be positioned within an insulating housing which is in turn attached to the electrical components. When used to interconnect printed circuit boards, that miniature elastomeric connector is positioned within a longitudinally extending recess in an insulating housing and the insulating housing is attached directly to the printed circuit boards. Although the circuit traces on the exterior of that miniature electrical connector have a width less than the spacing of conventional contact pads on printed circuit boards, in order to prevent easy alignment, it is still necessary to rely upon the housing to position the connector relative to the printed circuit board.
One example of an unshielded electrical connector which was in part intended for interconnecting relatively widely spaced boards is disclosed in U.S. Pat. No. 4,057,211. That connector also employs a thin film having circuit traces disposed on its exterior and uses elastomeric members to establish contact pressure when the compressive force is applied thereto. The miniature electrical connector disclosed in that patent also employs a central rigid body having a trough-like recess in which the elstomeric members are positioned. The thin film circuitry is, however, positioned along the rigid body and is to be held in position by a plurality of elastomeric members spaced side by side in the common recess. It can be appreciated that the assembly costs encountered with elasteromeric connectors of more conventional construction would be magnified for the electrical connector shown in U.S. Pat. No. 4,057,211, at least in part because of the large number of separate parts which must be employed.
U.S. Pat. No. 4,552,420 discloses a right angled connector for interconnecting circuitry on perpendicularly mounted printed circuit boards. However, each conductive trace on the flexible dielectric of the connector corresponds to a respective circuit pad on either the mother board or daughter board. Thus, one given connector can only interconnect circuitry that is on the same centerline spacing as the centerline spacing of the conductive traces on the flexible material. A change in centerline spacing on the mother board or daughter board requires a different connector having a corresponding centerline spacing on the flexible material.
Also, the conductive traces on the film are laterally staggered and surrounding the film such that every other trace occupies a different portion of the film, as best shown in FIG. 3 of U.S. Pat. No. 4,552,420. As shown in FIG. 2 of U.S. Pat. No. 4,552,420, and referring to the connector as a right triangle, a first trace 30a is a short trace extending only around the right angled portion. The next trace 30b is laterally staggered from the first trace 30a, and extends around the triangle from one perpendicular side to the other perpendicular side extending around the triangles hypotenuse.
The connector shown in U.S. Pat. No. 4,552,420 includes a means to control impedance, one method proposed is to include ground tracings on the inside surface of the film. In order to make a ground potential connection to the printed circuit boards, the ground tracings on the inside surface must be interconnected to the printed circuit boards. This is complicated by the fact that the film is densely filled with signal conduction paths disposed entirely around the film of the connector. One method proposed for making the ground potential connection between the ground traces and the circuit boards was to use some of the signal traces for signal return and interconnect the ground traces to those traces designated as signal returns, by means of a via.